System for vapor deposition of thin films

ABSTRACT

A method and apparatus is disclosed for vapor depositing a thin film of material on image retention surface substrate bodies comprising the steps of positioning a plurality of substrate bodies on a plurality of elongated, horizontally extending support mandrels, rotating each of said mandrels about an associated longitudinal axis thereof while simultaneously transporting said plurality of mandrels in an annular path about a horizontal axis, establishing an evacuated atmosphere about said assembly of mandrels, and vaporizing a material which is positioned in a planar array of crucibles located within a path defined by the annular travel of said mandrels.

United States Patent Erhart et al.

SYSTEM FOR VAPOR DEPOSITION OF THllN FILMS Inventors: Francis J. Erhart,Webster; Harold H. Schroeder, Rochester, both of NY.

Xerox Corporation, Stamford, Conn.

Filed: Sept. 25, 1973 Appl. No.: 400,593

Related US. Application Data Division of Ser. No. 244,374, April 17,1972 abandoned.

Assignee:

US. Cl. l18/49.1 Int. Cl. C23c 13/08 Field of Search 1l8/48-49.5,

References Cited UNITED STATES PATENTS 10/1956 Smith 118/49 Nov. 5, 19742,768,098 10/1956 Hoppe 118/491 X 2,912,351 11/1959 Danner et al.3,324,825 6/1967 Brumfield 3,796,182 3/1974 Roslev 118/48 PrimaryExaminer-Morris Kaplan 5 7 ABSTRACT A method and apparatus is disclosedfor vapor depositing a thin film of material on image retention surfacesubstrate bodies comprising the steps'of positioning a plurality ofsubstrate bodies on a. plurality of elongated, horizontally extendingsupport mandrels, rotating each of said mandrels about an associatedlongitudinal axis thereof while simultaneously transporting saidplurality of mandrels in an annularpath about a horizontal axis,establishing an evacuated atmosphere about said assembly of mandrels,and vaporizing a material which is positioned in a planar array ofcrucibles located within a path defined by the annular travel of saidmandrels.

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Pmtmmnnv 5 m4 3,845739 SHEET 08 [1F 10 min" wamm' 3 845 7339 am 51914PATENIEU SHEET 10 0F 10 ZZZ This is a continuation, division ofapplication Ser. No. 244,374, filed April 17, 1972, now abandoned.

This invention relates to an improved apparatus for the vapor depositionof a relatively thin film on a substrate body. The invention relatesmore particularly to an improved apparatus for fabricating anelectrostatographic plate by the vapor deposition of a photoconductivematerial on a substrate body.

In one form of electrostatographic reproduction system, a latentelectrostatic image is formed on an image retention surface and isdeveloped by contacting the surface with a developer material whichgenerally comprises a pigmented, electroscopic, thermoplastic resin.Attractive electrostatic forces cause the developer material to adhereto the latent electrostatic image in image configuration. The latentimage is subsequently transferred to a record medium such as a sheet orweb of paper to which it is fixed.

An image retention surface in this type of electrostatographicreproduction system generally comprises a relatively thin film ofphotoconductor material such as selenium or alloys thereof which isdeposited on an electrically conductive, substrate body. The filmpreferably has a thickness of about 55 to 60 microns. The substrate bodyis fabricatd of a metal which is formed as a drum or alternatively as aflexible endless belt. Generally, an interface is formed on thesubstrate body prior to deposition of the photoconductor material on thesubstrate body. The interface which is formed on the electricallyconductive substrate body functions to provide an electrically resistivebarrier between the photoconductor layer and the substrate. During imagereproduction, a uniform electrostatographic charge is initially formedon the photoconductor surface. The surface is then exposed to activatingelectromagnetic radiation in image configuration such as is provided byexposure to a light source through a phototransparency. Thephotoconductor material automatically alters the charge on its surfacein those areas which have been exposed to activating electromagneticradiation.

The quality of a reproduced image in an electrostatographic reproductionsystem of this type is dependent in part on the characteristics of thedeposited photoconductor film. This film should be substantially uniformin thickness and should exhibit uniform photoelectrical characteristicsacross its surface. Additionally, in order to provide uniformity ofimage reproduction in different electrostatographic machines, these filmcharacteristics should be substantially uniform over all such imageretention surfaces.

A photoconductor film has heretofore been formed on an electricallyconductive substrate body by the vaporization and deposition of thephotoconductor material on the substrate in an evacuated atmosphere. Thesubstrate body is initially cleaned and is then surface treated orcoated to establish the interface barrier thereon. Interface surfacetreatment is accomplished by coating or alternatively by heating thebody when the body is formed of materials such as aluminum. Thevaporization, deposition, and adherence of the photoconductor materialto the substrate is best effected when the substrate body is brought toan elevated temperature. This process has been practiced in the past bysupporting a substrate on an elongated mandrel and by rotating themandrel about an axis thereof which extends in a horizontal plane.Heating of the substrate body was accomplished by conveying a heatedliquid to the mandrel or alternatively by establishing a glow dischargebetween an electrode and. the substrate body. The mandrel is positionedadjacent an open crucible which extends coextensively with the length ofthe mandrel and contains a photoconductor material. This arrangement,while operative to produce useful image retention surfaces, is limitedin that the image retention surfaces thus produced exhibit variations inthe characteristics of the deposited film which in great part relate tothe characteristics of the associated crucible. Furthermore, thesetechniques do not readily lend themselves to a relatively economic and.high rate of production.

Accordingly, it is an object of this invention to provide an improvedmethod and apparatus for vapor depositing a relatively thin film ofphotoconductor material on a substrate body.

Another object of the invention is to provide an improved method andapparatus for producing an electrostatographic image retention surfacein a relatively economic manner and at a relatively high rate ofproduction.

Another object of the invention is to provide an improved method andapparatus for producing an electrostatographic image retention surfaceby vapor deposition in an evacuated chamber and which eliminates theneed for a preliminary formation of an interface surface on thesubstrate body.

Another object of the invention is to provide an improved method andapparatus for the production of an electrostatographic image retentionsurface which effects relatively efficient use of the photoconductormaterial.

Another object of the invention is to provide an improved method andapparatus for producing electrostatographic image retention surfaceswhich exhibit an improved uniformity in the thickness of the depositedfilm.

Another object of the invention is to provide an improved method andapparatus for producing electrostatographic image retention surfaceswhich exhibit improved uniformity in the electrical characteristics of adeposited film.

In accordance with features of the method of this invention, a pluralityof elongated horizontally orientated mandrels each supporting thereon aplurality of substrate bodies are each rotated about a horizontallyorientated longitudinal axis thereof and are transported-in a verticallyorientated path about a planar array of crucibles containingphotoconductor material. The photoconductor material is heated to atemperature for providing vaporization and deposition of the materialupon the substrate bodies.

In accordance with another feature of this invention, an electricdischarge is established between an electrode and the substrate bodiesfor forming an interface on said bodies and for preheating said bodiesto a desired temperature suitable for vapor deposition.

In accordance with other features of this invention,

an apparatus for depositing a relatively thin film on a substrate bodycomprises a vacuum chamber, a vertically orientated mandrel supportplate which is rotatably mounted about a horizontal axis, a plurality ofelongated, horizontal extending, rotatably mounted mandrels arrayed onthe mandrel support body and rotated therewith about a planar array ofcrucibles. Means are provided for rotating the mandrel support bodyabout its horizontal axis while simultaneously rotating each of themandrels about a longitudinal axis of the mandrel. The mandrels are eachadapted for receiving and supporting a plurality of substrate bodiesupon which a photoreceptor film is to be vapor deposited. In accordancewith other features of the apparatus of this invention, the vacuumchamber comprises a vertically positioned wall member and a bell shapedmember adapted to be transported into union with the wall member and toform a vacuum tight enclosure there with. The bell shaped vacuum memberencloses the rotatable mandrel support body and the mandrels mountedthereon. The planar array of crucibles are supported fron an inner wallsurface of the bell shaped vacuum chamber member and are positionedwithin a path of travel defined by rotation of the mandrels.

With the apparatus of this invention, electrostatographic imageretention surfaces are produced at relatively high rates and in arelatively economic manner with improved physical and electricalcharacteristics. Additionally, the processing of the substrate body isenhanced and an improved interface is established by simultaneouslyheating and forming the interface immediately prior to vapor deposition.

These and other objects and features of the invention will becomeapparent with reference to the following specification and to thedrawings wherein:

FIG. 1 is a side elevation view of an apparatus con- FIG. 6 is a view,partly broken away, taken along lines 6-6'of FIG. 4B;

FIG. 7 is an enlarged side view, partly broken away, of a portion of theapparatus of FIG. 4B;

FIG. 8 is an enlarged view, partly broken away, of a portion of theapparatus of FIG. 6;

FIG. 9 is a plan view of a planar array of crucibles employed with theapparatus of this invention;

FIG. 10 is a view of a portion of the vacuum chamber employed with theapparatus of FIGS. 1 and 4 and illustrating a crucible power supplyingmeans, a glow discharge power supplying means, a glow discharge powersupply means and temperature sensing and control equipment for theapparatus;

.FIG. 11 is a plan view of the crucible array of FIG. 9 illustrating theflow paths of crucible heating current therein; and,

FIG. 12 is a cross-sectional view of an arrangement for vapor depositinga film on a planar substrate body.

Referring now to the drawings, and more particularly to the embodimentof the apparatus of this invention shown in FIGS. 1, 2 and 3, there isillustrated a vacuum chamber 18 having a vertically orientated wallmember 20 which is secured in a stationary position by welding, forexample, to a vertical beam or wall body 22. The chamber enclosurefurther includes a generally bellshaped housing 24 having a vacuumflange member 26 mounted thereto. Electrical operating power is derivedfrom the sources 220, 232 and 518 (FIG. 10 and is coupled through thisflange to various components within the vacuum chamber. The vacuumchamber formed by the bell shaped member 24 and the verticallyorientated wall member 20 comprises a relatively large size chamberadapted for the mass production of image retention surfaces. The chambertypically has dimensions on the order of about 6 to 8 feet in diameterand I0 to 20 feet in length. It is constructed in accordance withconventional vacuum techniques for reducing the pressure within thechamber to values on the order of about l X 10' to l X 10 Torr. Apumping means, not illustrated, for pumping down the chamber to theselevels comprises a conventional vacuum system which includes a roughingpump, diffusion pumps and mechanical blowers.

A plurality of electrostatographic image retention surface substratebodies are positioned within the chamber 18 for vapor deposition of aphotoconductor on the surfaces thereof. As indicated in greater detailhereinafter, these substrate bodies are supported on rotatable mandrelswithin the chamber. In order to facilitate the placement and themounting of the substrate bodies within the chamber and in order toenhance the removal of these bodies subsequent to film deposition, thebell shaped vacuum chamber member 24 is adapted to be withdrawn fromunion with the wall member 20 for a distance sufficient for mounting anddemounting of the substrate bodies on the mandrels. The bell shapedmember 24 is formed, for example, of relatively heavy metal plate. Inorder to render it transportable in a longitudinal direction, thechambermember 24 is supported by a frame 28 to which are mounted rollerguides or wheels 30 which are aligned with and guided along a track 32.A drive means, not illustrated, is provided and is coupled to the frame28 for effecting motion of the frame and the supported member 24 alongthe track 32 for a distance sufficient for providing access to the freeend of the mandrels which are then exposed by the displacement of thischamber member.

A plurality of substrate bodies 40, 42, 44 and 46 are mounted on anelongated rotatable mandrel 48 which is adapted for rotation about itslongitudinal axis 49. Additional rotatably mounted mandrels 50, 52, 54,56 and 58 each having a plurality of substrate bodies mounted thereonare also provided. While six such mandrels each having four substratebodies mounted thereon are illustrated in the drawings, it will beappreciated from the discussion herein that the number of mandrels andthe number of substrate bodies which can be accommodated for vapordeposition can be varied.

The substrate bodies illustrated in FIGS. 1 through 3 are shown tocomprise in one embodiment relatively belt 59 is shown supported by apair of plastic, generally disc-shaped support form members 60 and 62which are positioned back to back and are secured together by means, notillustrated, in order to form a configuration which is adapted forsupporting the endless belt 59. The forms 60 and 62 each includeapertures formed centrally therein and through which the mandrel 54extends. A key means, not illustrated, secures this form assembly to theshaft 54 for rotation therewith. Longitudinal movement of the formassembly and its supported belts is restricted by a collar 64 which issecured to the shaft 54. An annular shaped coating mask 66 having aninwardly extending rib 68 is positioned on a surface of the inner belt.A similar mask 70 is positioned intermediate the belt 59 and an adjacentbelt 72. These masks function to define edges of the areas of depositedphotoconductor material on the belts, to space the belts on themandrels, and to reduce generally the deposition of photoconductivematerial upon the mandrel. While FIGS. 1-3 illustrate the positioning ofcylindrically shaped substrate belts in the chamber for the vapordeposition of a photoconductor material thereon, substrate supportbodies comprising cylindrically shaped drums may equally well bepositioned on the mandrels.

In addition to the cylindrical configuration thus far described, thesubstrate bodies can assume other configurations, as for example, aplanar configuration as is illustrated in FIG. 12. The substrate bodies51, 53, 55 and 57 of FIG. 12 are secured to surfaces of a support form61 by clamps or hold downs, not illustrated. The support form is frameshaped and includes spokes 63 extending from these surfaces to a hub 65.The hub is positioned on and keyed to a mandrel 67 for rotationtherewith.

A relatively efficient utilization of coating material, an enhancedrandomization of photoconductor deposition on the support substrates,and an improved control of deposited film thickness is effected byproviding a planetary rotational motion of the type wherein each of themandrels is rotated about its horizontally extending longitudinal axiswhile the rotating mandrels are transported in a path extending in asubstantially vertical plane. This desired epicyclic motion is effectedby the provision of a rotary support body referenced generally as 73which is formed by an annular shaped'disc 74 having a plurality ofradially extending arm segments 70-08 (FIG. 2) mounted thereto, such asby welding, and each of which supports hubs 90-100 respectively at adistal segment thereof. The arm segments are spaced apart and braced bystruts 102-112 which extend between adjacent arm members near the distallocated hub segments. Inner spacing and bracing struts 114-124 arepositioned adjacent the plate 74 and are welded to the plate and toadjacent radial arm members. The plate 74 includes a centrally locatedaperture 123 (FIG. 3) formed therein and into which a hub 124 extends.The hub 124 which is welded to the plate 74 is a member of a hollowrotary drive shaft which further includes a heavy walled tubular member126, a tubular shaft segment 120, a circular shaped plate 130, and acircular plate 132. These members are secured together by welding. Thetubular drive member 120 extends through the vertically orientatedvacuum chamber wall member 20 and through the backing wall or beam 22.There is mounted to an outer surface of the shaft 128 a pulley 134 whichis engaged by a drive belt 136. A primary source of rotary motioncomprising an electric motor 130 is provided and a drive pulley 139 ismounted on a drive shaft 140 of the motor. The drive shaft causesrotation of the plate 74 and results in the transport of hubs 90400 inan annular, and more particularly a circular, path extending in avertical plane within the chamber.

As indicated hereinbefore, each of the substrate body support mandrels4050 is rotated about its horizontally orientated longitudinal axis. Themandrels are each rotatably supported and driven at one end thereofwhile an opposite end of the mandrel provides for mounting of thesubstrate support forms and belts thereon. FIG. 3 illustrates one end ofthe mandrel 54 extending through the hub 96. Roller bearings and 152 arepress fitted near end segments of a sleeve 154 which is fitted into acylindrical bore in the hub 96. The mandrel 54 is thus rotatablymounted. A bevel gear 156 is mounted on the mandrel and is driveninorder to impart rotary motion about a horizontally orientated,longitudinal axis of the mandrel. A rotary force for rotating themandrel 54 is derived from a main bevel gear 150 and is coupled to themandrel gear 156 through a bevel gear 160, a drive shaft 162 which isjournaled in a body 164 and a bevel gear 166. The body 164 is welded tothe rotary plate 74. Each of the spindles in the apparatus are similarlyrotatably supported and derive rotation forces from the main bevel gear158.

Rotary motion is imparted to the main bevel gear 158 independently ofthe rotary motion of the plate 74 by a drive shaft which isconcentrically positioned with respect to the tubular shaped rotarydrive means which rotates the plate 74. The main bevel gear 158 issecured to the drive shaft 170 for rotation therewith. The shaft 170 isjournaled within the tubular member 120 and extends through bearings172, 174 and through the hub 124. A drive pulley 176 is mounted on thedrive shaft and is driven by a belt 178 from an electric motor source179 (FIG. 2). Thus, rotation of the drive shafts 120 and 170 result inan epicyclic motion of the substrate bodies. It is noted that themandrels and the main support plate 74 are independently driven andtheir rates of rotation can advantageously be independently varied.

During the vapor deposition process, it is desirable to monitor thetemperature of the substrate bodies. A thermocouple pickup junction 180is secured by spring loading means, not shown, to an under surface ofthe substrate body 59. Thermocouple leads 182 and 184 extend from thejunction 160, are fed through the substrate support body, through anaperture 186 in the tubular mandrel 54 and are dressed along an innersurface of the mandrel and are electrically coupled to slip rings 108and 190 which are mounted on the mandrel shaft. Pickup brushes 192 and194 are mounted in, and, are insulated from the sleeve 154 and leadsextending therefrom are dressed through an aperture 196 in the sleeve154 and through the hub 196 and are led to a thermal indicator andrecorder, not illustrated.

A means for supporting a photoconductor material within the chamber 18and for vaporizing the material comprises a planar array 200 ofcrucibles (FIG. 1) which are located within the vacuum chamber 18 andwhich are positioned within an annular path defined by the travel of thesupport mandrels. This planar array of crucibles is supported from anend wall segment 202 of the bell shaped housing member 24 and istransportable therewith. Thus, when the bell] shaped housing 24 isseparated from the wall member 20 the planar array of crucibles issimilarly withdrawn. As the bell shaped member 20 is advanced toward andis closed upon the wall member 20, the planar array is therebyautomatically positioned within the annular path defined by theepicyclic motion of the mandrels. An arrangement of the planar array ofcrucibles is described in greater detail hereinafter with respect to theembodiment of the apparatus disclosed in FIG. 4. For the present, it isnoted that in the apparatus illustrated in FIGS. 1-3, the array 200includes flanged support segments 204 and 206 which are mounted on aplate 208. The plate 208 is in turn supported on cross members 210 and211 which are secured to a support beam assembly 214. The beam assembly214 is mounted to a plate 216 which in turn is supported from thechamber wall segment 202. A support brace 220 extends between the beamassembly 214 and the plate 216. Although the array 200 of crucibles isshown to be centrally located within a circular path of travel of themandrels, the array can be positioned at locations displaced from thiscentral location. The crucible assembly can alternatively be locatedoutside the annular path defined by the travel of the mandrels.

Prior to closure of the vacuum chamber, each of the plurality of boatshaped crucibles 222 in the array 200 have deposited therein apredetermined amount of photoconductor material which is to be depositedon the substrate bodies. The photoconductor material comprises forexample selenium or alloys thereof.

Current conducting leads 224 and 226 extend from the chamber throughfeed through connections (FIG. 10) and are coupled to a crucibletransformer 228 to which a voltage is applied from a line source 220under the control of a temperature servo control means 232. The servocontrol 232 receives monitoring temperature information from one or moretemperature sensors, not shown, such as thermocouples attached to thecrucible array. The crucibles are made of a conductive material such asstainless steel and current flows therein thereby heating the crucibleassembly 200 and causing the assembly to heat both the substrate supportbodies which are transported within the chamber and the photoreceptormaterial. The temperature of the substrate bodies, which have arelatively low thermal mass and are supported by plastic forms having arelatively low thermal conductivity is increased to the desired coatingtemperature. The photoconductor material is heated to vaporization anddeposits upon the surfaces of the support body substrate. Thus, thecrucible assembly in addition to containing the photoconductor materialand causing its vaporization further operates to heat the substratesupport body to a desired temperature for satisfactory vapor depositionof the photoconductor material on the surface of the substrate.

Photoconductor alloys suitable for use with the present inventioninclude, without limitation, selenium alloyed with arsenic, tellurium,thallium, antimony, bismuth and mixtures thereof. U.S. Pat. Nos.2,803,542; 2,822,300; 2,745,327; 2,803,541; 2,970,906; and 3,312,548illustrate in more detail suitable applications and process techniquesfor selenium and selenium alloys which may be used in carrying out theprocess or in using the apparatus of the instant invention. Aparticularly preferred photoconductive alloy suitable for use in theinstant invention comprises selenium alloyed with arsenic in the rangeof from about 0.1 to 50 weight percent. U.S. Pat. Nos. 2,803,542;2,822,300 and 3,312,548 more fully define such alloys and areincorporated herein by reference. Generally, when selenium is alloyedwith arsenic, the vapor deposited photoconductive layers of such alloysexhibit an inherent fractionation which is characterized by acomposition gradient in which greater concentrations of arsenic arefound at the free surface of the alloy layer with the concentration ofthe arsenic decreasing towards the photoconductor-substrate interface.In using the process and apparatus of the instant invention, it has beenobserved that for very low arsenic concentrations (i.e.,

0.1-0.75 wt. As balance selenium), that a relatively flat concentrationgradient for the arsenic results.

In a typical coating operation, the substrate support bodies eachcomprise an electroformed, flexible, endless belt which is formed ofnickel and which has a thickness of about 4.5 mils, a diameter of about20 inches and a width of about 16% inches. The substrate support bodiesare cleaned and an organic interface, for example, is formed thereon bycoating. The belts are initially mounted on the support forms which arefabricated of a material which offers sufficient support for preventingphysical damage to the relatively delicate thin walled substrate,provides a thermal barrier for reducing the transfer of heat between thesupport and the substrate and is compatible with the vacuum process.Suitable materials from which these forms are fabricated comprisepolypropolene and polystyrene. The coating masks which can be fabricatedof plastic or metal are positioned on an edge of a form and the form isthen mounted on the mandrel shaft. A plurality of such assemblies aremounted on the mandrel until the mandrel is loaded to capacity. Aphotoconductor material which comprises for example an alloy of seleniumand arsenic is deposited in the individual boat shaped crucible members.It is noted that the loading process is greatly facilitated since thebell shaped member 24 which is withdrawn from the wall 20 and beyond thedistal end segments of the mandrels provides ready access for theoperator in performing the mounting operation. Further, the removal ofthe boat array from that area within the path traveled by the mandrelsduring the coating operation facilitates charging of the boats. The bellshaped member 24 is then closed upon the wall member 20 and theplanetary motion of the mandrels is initiated by energizing the motors138 and 180 [I G. 2]. Typically, the tubular shaft assemblyand the plate124 mounted therefrom rotates at a rate of about 5 RPM. and the mandrelsrotate at a rate of about 15 RPM. The vacuum pumping means is then ac-.tivated and pump down proceeds until a pressure on the order of about 5X 10 Torr is attained. Crucible power is then applied to the crucibleassembly from the transformer 228 (FIG. 10) under the control of a timetemperature control means 232. Prior to heating of the crucibleassembly, the substrate bodies are at a temperature of about 25C. Thetemperature control means 232 is adapted to increase the temperature ofthe crucible and of the substrate bodies in accordance with apredetermined temperature program. This means includes a closed loopcontrol system which derives temperature indications from sensorslocated within the chamber. Temperature control and programming means ofthis type are well known in the art. During deposition, the temperatureof the substratebodies rises to a value within a range of about 85C. Atthis temperature, an acceptable photoconductor film is deposited whichexhibits both desirablephysical and electrical characteristics. Thecrucible will be maintained at the programmed temperature until theproper thickness of photoconductor material has been vapor depositedupon the substrate body. This is controlled by the amount ofphotoconductor material deposited in the crucibles, the time-temperatureprogram provided by the control means, and the pressure within thechamber. When the proper thickness has been attained, crucible power isdecoupled, the crucibles are cooled, and the chamber is then returned toatmospheric pressure.

In a typical operation, the cycle of events will include a vacuumpumping interval of about 9.5 minutes, a crucible heating interval ofabout 40 minutes, a dwell time of about 6 minutes during which time thetemperature of components within the chamber decreases, and f1- nally adepressurization interval of about 6 minutes during which the chamber isreturned to atmospheric pressure.

The apparatus and method described herein advantageously provides forthe simultaneous coating of a relatively large number of substratebodies thereby providing a relatively efficient, economic, and highproduction capacity system. In addition, the planetary motion of thesubstrate bodies within the vacuum coating chamber requiressubstantially less coating material than prior techniques for anequivalent thickness. A relatively high degree of randomization ofdeposition occurs which enhances its uniformity of coating betweendifferent substrate support bodies. Quality control of the producedelectrostatographic image retention surfaces is thereby greatlyenhanced. For example, a photoconductor thickness measurement need onlybe taken on a deposited film associated with a single mandrel and thiseffectively measures the entire batch of photoreceptors. Not only is theuniformity of photoreceptor production enhanced but the labor involvedin quality control of the photoreceptor is thereby reduced.Additionally, control of photoconductor thickness within a particularphotoreceptor is more precise than prior arrangements. In addition tothe advantageous uniform thickness of the characteristics attending therandomization provided by planetary coating, improved electricalcharacteristics of the photoreceptor are also realized in that theuniformity of electrical properties between different coatings isenhanced.

An alternative embodiment of an apparatus constructed in accordance withfeatures of this invention is illustrated in FIGS. 4-11. Those elementsof FIGS. 4-11 which perform functions similar to those performed byelements of FIGS. 1-3 bear the same reference numerals. In theembodiment of FIGS. 4-11, a plurality of mandrels 400, each of which arehorizontally orientated are rotatably supported at one end thereof by aplate 402 (FIG. 4A). This plate is mounted on a drive shaft 404 and isjournaled through the vertical wall plate and its support beam 22 to apulley 406 which is secured to an end of the shaft. The pulley iscoupled via a drive belt 400 to a drive pulley 410 which is mounted on adrive shaft of a motor 412. Excitation of the motor 412 causes rotationof the drive pulley and a corresponding rotation of the plate 402. Aring shaped body 414 having a plurality of hubs 416 formed therein ismounted to and secured to the plate 402 for rotation therewith. Thehubs, which are positioned in an annular array, each include ahorizontally extending cylindrical bore 417 which functions as a journalfor the mandrels 400 extending therethrough. A relatively large diameterspur gear 418 having gear teeth 419 formed on its peripheral surface isjournaled about a segment 420 of the drive shaft 404. Longitudinalmotion of the gear 10 is restricted by a drive shaft segment 422 ofenlarged diameter and a collar 423.

The gear 410 is therefore free to rotate independently of the rotationof the plate 402. The spur gear 418 includes an integral hub segment 423having gear teeth 421 formed about a peripheral surface of the hub 423.The hub 423 is engaged and driven by a spur drive gear 424 which ismounted on a shaft 426. The shaft 426 which in FIG. 4A is shown bydashed lines extends through the vacuum chamber wall member 20 and thebackup beam 22 and includes a pulley, not illustrated, mounted on anouter segment thereof which is driven by an electric motor 425 (FIG. 5).Each of the mandrels 400, which extend through a cylindrical bore 417 inthe ring 414, has mounted to an end thereof a spur gear 420 whichengages the gear teeth 419 of the gear 418. The plate 402 and theplurality of mandrels 400 are thus independently rotatable therebyadvantageously providing means for independently altering their speedsof rotation.

The planar array 200 of crucible members which was referred tohereinbefore is formed by a plurality of boat shaped crucible members222 (FIGS. 9 and 11). Each of these members includes flanged endsegments 449 (FIG. 7) which are welded or bolted to the flanges of othermembers in order to form a. plurality of cruible strips 450-467 (FIG.11). The strips 450-459 extend substantially coextensively with themandrels 400 while relatively shorter outrigger crucible strips 460-467are provided and are positioned near ends of the array for assuringdistribution of vaporized photoconductor material near opposite endportions of the vacuum chamber. The crucible members 222 are typicallyfabricated of stainless steel. Each of the crucible strips are supportedabove an associated longitudinally extending strip 203 by flange members209 (FIG. 7) which are located along the length of a crucible strip. Inaddition, ceramic insulating spacers 468-471 are provided and aremounted to a flange 206 and a support block 207 at opposite ends of eachstrip for providing electrically insulated support and electricalterminations for the crucible strips. The strips 208 are mounted to asupport strip 211 which extends in a direction normal to the strip andis secured to the beam 214. The beam 214 which comprises a rectangularshaped channel is welded to a plate 215 which in turn is mounted to aplate 216. The plate 216 is supported from an extending mount 210 wichis secured to an inner wall segment 202 of the vacuum chamber member 24.A brace 220 extends between the beam 214 and the plate 215 for providingadditional support for the beam 214.

Heating current is applied to the planar array 200 of crucibles from thecrucible transformer 228 (FIG. 10) under the control of the servotemperature control means 232. Current flows from this transformer viavacuum feed-throughs to the outrigger strips 464 and 467 of the planararray (FIG. 11).. Adjacent crucible strips are strapped together byrelatively heavy, flexible, conductive webbing 484 as best illustratedin FIGS. 6 and 0 in order to provide a series current flow'path throughthe crucible strips of the array. The strapping arrangement and thecurrent flow paths resulting therefrom are illustrated in FIG. 11 forone alternation of an ill AC cycle by the directions of the arrows shownin the figure. This flow of current, as indicated hereinbefore, heatsthe crucible array and the substrate bodies and causes vaporization anddeposition of the photoconductor material upon the substrate bodies. Thecurrent is applied in accordance with a predetermined timetemperatureprogram in order to attain the desired variations in temperature and tothereby control the thickness of the photoconductor material which isdeposited on the substrate bodies.

In accordance with another feature of this invention, means are providedfor preheating the substrate bodies during their planetary travel withinthe chamber. This means is shown to comprise a plurality of glow barassemblies 500-506 (FIGS. 6, 7 and 8). A relatively high potential isapplied to the cathode of the glow bar assemblies causing a discharge inthe space between the glow bars and the support substrate bodies whichresults in at least two advantageous effects. In addition to heating therotating substrate support bodies which are transported in an annularpath past the glow bar assemblies (FIG. 6) to the desired temperaturesfor the deposition of the photoconductor material, the glow barassemblies in the case of certain substrate body materials, such asaluminum,.establish an interface surface on the substrate supportbodies. This process then advantageously eliminates the need forpreliminary processing the substrate support bodies by forming aninterface surface thereon. Furthermore, it has been found that theestablishment of this interface at a time immediately prior to thedeposition of the photoconductor in an evacuated atmosphere results inan enhanced photoconductor characteristic over that provided by priorart apparatus wherein the interface was formed in ancillary apparatusand was then subjected to an additional time interval and handling underatmospheric conditions.

The glow discharge assemblies 500, 502, 504 and 506 each include andelectrode comprising an elongated, electrically conductive glow barmember 508 which is positioned adjacent the annular path of travel ofthe rotating mandrels 400. The glow bar member is spaced a radialdistance from the mandrels 400 by adjustable spacing means for providingthe desired discharge. The discharge will be dependent upon such factorsas the amplitude of the potential applied to the glow bar, the chamberpressure, the nature of the residual gas in the chamber and the shape ofthe cathode. The electrode member 508 extends longitudinally andcoextensively with the length of the mandrels 400. It is supported atopposite ends by electrically insulating retaining plates 510 and 511(FIG. '7) formed of ceramic for example. The glow bar is supported atlocations along its length by a plurality of retaining means 512 each ofwhich includes a screw member which extends between the glow bar and anelongated support plate 513. The retaining means 512 also includeselectrical insulating spacers for insulating the relatively highpotential of the glow bar from the plate 513. Glow discharge shields 515are secured to the plate 513 such as by welding and extend in adirection normal to the plane of the glow bar. These shields function toshield and confine the glow discharge to the space immediately below theglow bar electrode 508. The plate 513 is secured to an elongated rail520 which has welded thereto, extensible radially adjustable supportarms 522. These support arms each include slots 523 extendinglongitudinally and are adjustably mounted'by screw pairs 524 whichextend through the slots 523 and through apertures 525 in the supportplates 526 and 527.. The aperture pairs are positioned circumferentiallyabout the support plates thereby providing for both radial andcircumferential adjustment of the glow bars. These support plates aremounted to a channel shaped frame body 528 which is rigidly mounted toand suspended from the beam 214 by extending arms 530. Stiffner rods 529and 53]. extend between and are welded to the plates 526 and 527. Anelectric potential is applied to the glow bar member 508 through a lead530 which is coupled to each of the glow bar members through a vacuumsealed feed from the power source 518 (FIG. 10).

In operation, the bell shaped chamber 24 (FIG. 4B) is withdrawn fromunion with the wall member 20 (FIG. 4A). The chamber member 24 iswithdrawn beyond the distal segments 600 of the mandrels 400 forproviding access for mounting a plurality of tubular shaped substratebodies 602 on each of the mandrels. A plurality of edging masks 604 areprovided and positioned between the substrate members on a mandrel inorder to define an edge for the deposited coating. In a typical example,the substrate body 602 comprises a tubular body formed of aluminum andhas a nominal diameter of about 3 /2 inches, a length of about 16inches, and a wall thickness of about three-sixteenths of an inch. It isnoted that the substrate bodies need only have been previously cleanedbefore mounting on the mandrels. The boats of the crucible array arecharged with a photoconductor material, referred to in detailhereinbefore. The bell shaped housing member 24 is then advanced intocontact with the wall member 20 in order to provide a vacuum tight seal.The electric motors are energized in order to rotate shafts 404 and 426and to initiate the planetary motion of the substrate bodies within thechamber. A vacuum pumping operation is initiated by activating thevacuum pumping means. In a typical example, the plate 402 is rotated ata rate of about 5 RPM and the mandrels 400 are rotated at a rate ofabout 15 RPM. Pump down of the chamber proceeds until the chamberpressure has reached a value on the order of 10 to 50 milli-Torr. Thischamber pressure, when established, is maintained by a pressure sensingtransducer which operates in conjunction with the vacuum pumping means.A gas is admitted to the chamber by a control leak during this period oftime. The gas can comprise air which has been conveyed through amoisture removing device. Other gases such as oxygen may also beemployed. With the chamber pressure maintained within the desired range,the glow discharge process is initiated. A voltage of between 1,000 and5,000 volts is applied to the electrode elements which establishes ahigh voltage plasma between the glow bar cathodes and the substrate bodyanodes. This plasma discharge preheats the substrates prior toinitiation of the vapor deposition of the photoconductor material on thesubstrates. Additionally, the

plasma discharge functions to establish an interface on the aluminumsubstrate by forming a thin aluminum oxide film on the outer surfaces ofthese bodies. The plasma discharge continues until a substratetemperature on the order of about 40C. to about C. is attained. Thecontrol leak is shut off and pump down is again initiated in order toreduce the pressure within the chamber to a pressure on the order ofabout 5 X 10' Torr or less. Electrical power is then applied to thecrucible assembly for heating the crucibles and causing vaporization ofthe photoconductor material contained therein. The closed looptemperature control means 232 provides for controlling the temperatureof the crucible in a programmed manner. Power is applied to the cruciblefrom the alternating power source 220 through the transformer 228 underthe control of temperature programm control means 232. The substratetemperature then generally exhibits an increase in tem' perature ofabout C. to C. during the application of power to the crucible assembly.Power will be applied under program control until the desired alloythickness is established. At this time, power to the crucible assembliesis interrupted and a cooling dwell time is provided. The vacuum chamberis then returned to atmospheric conditions.

In a typical cycle of events, the initial evactuating operation isperformed in 12 minutes; the glow discharge is performed in 10 to 55minutes; the further reduction in vacuum within the chamber occurs inabout 1 minute; the power is applied to the crucibles for between about25 to 60 minutes; the temperature cooling dwell time is about 5 minutes;and the pressurization to atmospheric pressure occupies approximately 5minutes.

The embodiment of this invention described with respect to FIGS. 4-11 isparticularly advantageous in that it eliminates the need for thevpreliminary formation of an interface on the substrate bodies. inaddition to eliminating this step, the interface formed by this methodprovides improved characteristics in the photoreceptor since theinterface is formed under evacuated conditions immediately prior todeposition of the photoconductor material and further handling andexposure at atmospheric conditions is avoided.

There has thus been described an improved method and apparatus forfabricating an electrostatographic image retention surface by the vacuumdeposition of a photoconductor material on a substrate support body. Themethod and apparatus provides for the epicyclic motion of a plurality ofsubstrate bodies which are horizontally orientated on a rotatingmandrel. A plurality of such mandrels are provided and a relativelylarge number of substrate bodies are thereby rotated while they aresimultaneously coated by the evaporation and deposition of thephotoconductor material. Additionally, a glow discharge means isprovided which establishes an interface on the substrate body, whichpreheats the body to operating temperatures prior to vacuum deposition,or which both forms the interface and preheats the body. The describedmethod and apparatus are advantageous in that an improved distributionof photoconductor material is provided for a useful range of filmthicknesses; a more efficient use of the graphic image retentionsurfaces.

While there has been described a particular process and apparatus forcarrying out the invention, it will be understood that variousmodifications may be made thereto without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:

l. Apparatus for the vapor deposition of a layer of material onsubstrate bodies comprising:

a generally vertically oriented support table adapted for rotation abouta horizontal axis;

means for rotating said support table;

a plurality of elongated horizontally oriented mandrels rotatablysupported in an annular array on said support table;

means for rotating each of said mandrels about a longitudinal axisthereof;

each of said mandrels adapted for receiving, supporting, and rotatingtherewith a plurality of substrate bodies;

means for vaporizing a predetermined quantity of material which is to bedeposited upon said substrate bodies;

heating means including an electrode mounted and adjustably positionedadjacent. the annular path of travel of said mandrels and extendingsubstantially coextensively with the elongated mandrels, means forapplying an electric potential between said electrode and said substratesupport bodies for establishing a glow discharge between said electrodeand said substrate support bodies for forming an interface barrier layeron said support bodies; and

within an annular path of travel of said mandrels.

* =i= l= l UNITED STATES PATENT OFFICE H CERTIFICATE OF CORRECTIONPatent No. 3, 845, 739 Dated November 5 1974 Inventor(s) Francis J".Erhart and Harold H. Schroeder It is certified that error appears in theabove-identified. patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 4, eliminate "continuation".

Column 4, line 1, "18" should be -1.

Column 5, line 43, "73" should be 7 3 Column 6, line S9, "200" should be2 0 0 Column 7, lines 9, 17, 24 and 39, "200" should be --g g--.

Column 10, lines 25 and 55 "200" should be +-2oo--.

Signed and sealed this 14th day of January 1975.

(SEAL) Attest: I

M COY M. GIBSON JR. 0. MARSHALL DANN A testing Officer Commissioner ofPatents (149) USCOMM-DC wan-Pea ".5. GOVIRH'ENT PRINTING OFFICE 2 I9.0"!33.

1. Apparatus for the vapor deposition of a layer of material onsubstrate bodies comprising: a generally vertically oriented supporttable adapted for rotation about a horizontal axis; means for rotatingsaid support table; a plurality of elongated horizontally orientedmandrels rotatably supported in an annular array on said support table;means for rotating each of said mandrels about a longitudinal axisthereof; each of said mandrels adapted for receiving, supporting, androtating therewith a plurality of substrate bodies; means for vaporizinga predetermined quantity of material which is to be deposited upon saidsubstrate bodies; heating means including an electrode mounted andadjustably positioned adjacent the annular path of travel of saidmandrels and extending substantially coextensively with the elongatedmandrels, means for applying an electric potential between saidelectrode and said subStrate support bodies for establishing a glowdischarge between said electrode and said substrate support bodies forforming an interface barrier layer on said support bodies; and meansproviding an evacuated enclosure for said heating means, mandrels, andthe substrate bodies supported thereon.
 2. The apparatus of claim 1wherein said means for vaporizing said material is positionedsubstantially outside an annular path of travel of said mandrels.
 3. Theapparatus of claim 1 wherein said means for vaporizing said material ispositioned substantially within an annular path of travel of saidmandrels.